Stereo loudspeaker system

ABSTRACT

A stereo loudspeaker system with right-hand and left-hand loudspeaker sections each having forwardly and rearwardly directed loudspeaker means fed with middle and high-frequency signals of the associated stereo channel, the rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to a horizontal plane and a vertical plane extending transversely to the vertical sound reflecting wall in a room in front of which the loudspeaker system is placed. Means are provided for selectively orienting the asymmetric pattern of the rearwardly directed loudspeaker means so the pattern is directed principally laterally inwardly or principally outwardly of said vertical plane.

Unite States Patent Frederick W. Nichols [72] lnventor South Bend, 1nd.[21] AppLNo. 850,949

[22] Filed [45 1 Patented [73 Assignee Aug. 18, 1969 Dec.'l4, 1971Electra-Voice, Inc. Buchanan, Mich.

54 1 STEREO LOUDSPEAKER SYSTEM 24 Claims, 30 Drawing Figs.

s21 u.s.c1 179/1011, l79/lE,l8l/31B s11 1m.c1 ..G10kl1/00 501 Field atSearch 179 1 E, 1

G, 1 GA, 1 AT; 181/31 B [56] References Cited UNITED STATES PATENTS10/1934 Goshaw 2,710,662 6/1955 Camras.... 2,921,135 1/1960 HoodwinPrimary Examiner -Kathleen l-l. Claffy Assistant Examiner-Douglas W.Olms AttorneyWallenstein, Spangenberg, Hattis & Strampel ABSTRACT: Astereo loudspeaker system with right-hand and left-hand loudspeakersections each having forwardly and rearwardly directed loudspeaker meansfed with middle and high-frequency signals of the associated stereochannel, the I rearwardly directed loudspeaker means of each loudspeakersection providing an overall directive sound pattern which isasymmetrically related to a horizontal plane and a vertical planeextending transversely to the vertical sound reflecting wall in a roomin front of which the loudspeaker system is placed. Means are providedfor selectively orienting the asymmetric pattern of the rearwardlydirected loudspeaker means so the pattern is directed principallylaterally inwardly or principally outwardly of said vertical plane.

PATENTEDUEBMISYI 352194 sum 2 [IF 5 JIIIIIIIIIIIII :mIIII'IIIIIIImPATENTEDBECMISII 3527,945

saw 3 nr 5 PATENIEU DEC I 4 I971 ALL FREQ 6455 dlvLy liuenz fi' ALL ,jiedem/ MJVM wZJ STEREO LOUDSPEAKER SYSTEM This invention relates tostereo loudspeaker systems and particularly to such systems which havetheir primary utility for home entertainment applications.

lt has been, heretofore, recognized that dispersion and/or reflection ofat least a portion of the directive middle and high frequencies of astereo system, can under certain conditions, provide an enhanced, moredesirable effect in comparison to a stereo system which directs soundonly forwardly into the room. Accordingly, some stereo loudspeakersystems have, heretofore, directed middle and high-frequency signalsagainst the vertical wall in front of which the loudspeaker system ispositioned. Most of these systems provide an overall rearwardly directedsound pattern which is symmetrical with respect to a vertical planeextending transversely of the sound reflecting wall so that sound isdirected rearwardly in all directions. Since such a sound patterndistributes sound in such a way that the sound from each stereo channelreaches the observer from all directions, the stereo effect isdiminished.

In some stereo loudspeaker systems the directive middle and highfrequencies are directed rearwardly and laterally outwardly in a patternsymmetrical with respect to a horizontal plane. However, when sound isdirected rearwardly against a vertical sound reflecting wall onlysymmetrically with respect to a horizontal plane, the spacing of thespeaker units from the wall' generally must be substantial to avoidsound interference problems and the propagation of sound laterallyoutwardly near the sidewalls of a room can frequently cause undesirableresonance effects, depending upon the geometry of the room and therelationship of the loudspeaker system thereto.

Thus, a given loudspeaker system may produce highly effective resultsunder one set of room geometry and loudspeaker placement conditions andbe completely unsatisfactory with another room geometry or loudspeakerplacement condition. Also, a given desired furniture arrangement maylimit the physical separation of stereo loudspeaker units to a pointwhere such spacing is too far apart or too close for the proper stereoeffect. In this connection also, it has been discovered that orchestralrecordings sound more like live performances when a wide lateral outwardangle of dispersion of the sound is effected and small ensemblerecordings sound more like a live performance when a narrow angle ofdispersion of the sound is effected.

Accordingly, uncontrolled dispersion and/or reflection of sound withinthe listening environment often creates unsatisfactory soundreproduction for a given recording due to effects from geometry andconstraints on the placement of the loudspeakers due to furniturearrangement problems in the room involved.

Accordingly, the objects of the invention involve the provision of astereo loudspeaker system which overcomes one or more of the variousproblems referred to above. More specifically, an object of theinvention is to provide an improved stereo loudspeaker system which caneasily and readily be adapted to a wide variety of room geometry, musicrecording type, loudspeaker placement limitations and other variableconditions. A related object of the invention is to provide aloudspeaker system which can provide a desired stereo effect whethernear normally obstructing pieces of furniture or where the loudspeakerunits involved must be spaced abnormally close together or far apart orclose to the sidewalls of a room.

Another object of the invention is to provide a stereo loudspeakersystem as described which can be manufactured at a relatively low cost.A related object of the invention is to provide a stereo loudspeakersystem as described which includes relatively small and lightweightspeaker units which can be placed on tables and bookshelves as well ason the floor.

Still another object of the invention is to provide a stereo loudspeakersystem as described utilizing cone loudspeaker units and where a maximumtotal loudspeaker cone area operative at low frequencies is achievedwhile accomplishing the other objectives of the invention described.

In accordance with one of the aspects of the invention, each of themirror-image loudspeaker sections of a stereo loudspeaker systemincludes loudspeaker means for radiating directive middleandhigh-frequency sounds preferably symmetrically forwardly into thelistening area, and loudspeaker means for directing these frequenciesrearwardly against a vertical sound reflecting wall of a room in arearwardly directed sound pattern which extends principally laterallyoutwardly or principally laterally inwardly of a vertical plane passingthrough the sound pattern extending transversely to the sound reflectingwall. Where, in a given room-arrangement, it is most effective to placethe directive stereo loudspeaker sections involved abnormally closetogether, the rearwardly directed overall asymmetric sound patterndescribed is oriented principally laterally outwardly, and, where it ismost effective to place the stereo loudspeaker sections abnormally farapart or near the sidewalls of a room, the rearwardly directed overallasymmetric sound pattern is oriented principally laterally inward. I

A further advantageous feature of the invention is in arranging therearwardly directed loudspeaker sections so that the overall directivesound patterns thereof are asymmetric both with respect to the saidtransverse vertical plane and a horizontal plane passing through eachoverall directive sound pattern so that, for example, when the speakersections are supported on the floor, a table or a low portion of abookshelf, the asymmetric sound pattern inclines upwardly as well aslaterally outwardly or inwardly as the case may be. In such case, theloudspeaker sections may be placed much closer to the sound reflectingwall in comparison, for example, to an orientation where the rearwardlyradiated sound is directed in a horizontal direction or plane.

In accordance with the most advantageous form of the invention, where itis desirable to minimize the cost and the size of the stereo loudspeakersystem, all of the forwardly and rearwardly directed middleandhigh-frequency loudspeaker means of each stereo loudspeaker section arecontained within a relatively small common enclosure which is portableand lightweight, so that it can be readily supported on a table orbookshelf and be moved about with ease. in its most preferred form, thecommon enclosure for each loudspeaker section has a truncated cubicshape with a front baffle-forming wall with an opening therein behindwhich a cone loudspeaker is mounted for directing sound forwardly intothe listening area, and a pair of rearwardly facing, truncating,baffle-forming walls at the rear thereof in at least two planes whichmake an obtuse angle with respect to one another. The truncatingbafile-forming walls have openings behind which cone loudspeakers aremounted for directing sound along axes which make an acute angle withrespect to one another.

The loudspeaker units now being described for the two stereo channelsare mirror images of one another relative to a centered vertical planeextending transverse to the sound reflecting wall of the room involvedmidway between the loudspeaker sections. The cone loudspeakers mountedbehind the truncating baffle-forming walls form overlapping directivesound patterns which, in one orientation of the enclosure, areprincipally horizontally spaced to provide an overall fanshaped soundpattern facing generally horizontally and, in another orientation of theenclosure, are principally vertically spaced to form an overallfan-shaped pattern facing generally vertically. These overall fan-shapedsound patterns are rearwardly and laterally inwardly or rearwardly andlaterally outwardly directed depending upon whether each enclosure isused as a right-hand or a left-hand enclosure for the stereo soundsystem involved. There are thus provided four different possible soundpattern configurations to adapt the loudspeaker system to a variety ofdifferent environmental conditions.

In a more sophisticated form of the invention which provides a betterlow'frequency response and a selection of different directive soundpatterns electrically without moving the loudspeaker enclosures around,each of the loudspeaker enclosures preferably has one or moreloudspeakers mounted on a front vertical baffle-forming wall fordirecting sound forwardly directly into the listening area, a first pairof mirrorimage related, rearwardly and upwardly facing baffle-formingwalls facing in opposite lateral directions at the right-hand andleft-hand ends of the loudspeaker enclosures and a central rearwardlyand upwardly facing baffle-forming wall interconnecting theabove-mentioned mirror-image related baffleforming walls. Mostadvantageously, the first pair of mirrorimage related baffle-formingwalls are intersected at the bottom thereof by a second pairof'mirror-image related, rearwardly facing walls formed in generalvertical planes facing in opposite lateral directions. Cone loudspeakersare mounted on all the aforementioned rearwardly facing baffle-formingwalls to direct sound through openings therein. The low frequencies ofthe stereo channel involved are fed at all times to all of theloudspeakers in each enclosure so maximum lowfrequency response, whichis partly a function of the total cone area of the various loudspeakers,is achieved. The selection in the directivity pattern is achieved by theuse of lowpass filters which are connected selectively to various onesof the rearwardly directed cone loudspeakers. The loudspeakers whichhave no low-pass filters connected thereto will generate directivemiddleand high-frequency sound patterns along their axes.

The above-mentioned and other features and advantages of the inventionwill become apparent upon making reference to the specification tofollow, theclaims and the drawings wherein:

FIG. 1 is a view of the end of a room with a pair of stereo loudspeakerunits constituting the most preferred form of the invention positionedrelatively close together;

FIG. 2A and 2B are respectively rear perspective views of the twoloudspeaker units shown in FIG. 1;

FIG. 3 is a transverse sectional view through the loudspeaker unit shownin FIG. 2B, taken along section line 3-3 thereof;

FIG. 4 is a side elevational view of the stereo loudspeaker system shownin FIG. 1;

FIG. 5 is a view of a different room arrangement than that shown in FIG.1 where the loudspeaker units are relatively widely spaced apart nearthe sidewalls of the room;

FIG. 6A and 6B are respectively rear perspective views of theloudspeaker units shown in FIG. 5;

FIG. 7A is a plan view of the loudspeaker units shown in FIG. 1 with theindividual sound directivity patterns of each cone loudspeaker thereindiagrammatically indicated, the loudspeaker units being oriented in sucha way that the rearwardly directed cone loudspeakers are spaced apartprincipally in a horizontal direction to provide an overall horizontallybroadened directive sound pattern directed principally laterally,outwardly and upwardly of the speaker units;

FIG. 7B is a side elevational view of the left-hand loudspeaker unit ofFIG. 7A with the individual directive sound patterns of the coneloudspeakers diagrammatically indicated;

FIG. 8A is a plan view of the loudspeaker units of FIG. 1 reoriented sothat the left-hand and right-hand loudspeaker units of FIG. 7A are theright-hand and left-hand loudspeaker units in FIG. 8A anddiagrammatically showing the individual directive sound pattern of eachcone loudspeaker thereof, the rearwardly directed ones jointly providingan overall horizontally broadened sound pattern for each loudspeakerunit directed principally laterally inwardly and upwardly of theloudspeaker unit;

FIG. 8B is a side elevational view of the left-hand loudspeaker unit ofFIG. 8A with the individual directive sound patterns of the coneloudspeakers diagrammatically indicated;

FIG. 9A shows the loudspeaker units of FIG. 7A reoriented by tilting theright-hand and left-hand loudspeaker units 90 laterally inwardly so thatthe rearwardly directed cone loudspeakers and the individual sounddirectivity patterns thereof diagrammatically indicated are principallyvertically spaced to provide an overall vertically broadened soundpattern for each loudspeaker unit directed principally laterallyinwardly and upwardly of the loudspeaker unit;

FIG. 9B is a side elevational view of the left-hand loudspeaker unit ofFIG. 9A with the individual directive sound patterns of the coneloudspeakers diagrammatically indicated;

FIG. 10A is a plan view of the loudspeaker units shown in FIG. 9Areoriented so that the left-hand and right-hand loudspeaker units ofFIG. 9A are the right-hand and left-hand loudspeaker units in FIG. 10Aand diagrammatically showing the individual directive sound pattern ofeach cone loudspeaker thereof, the rearwardly directive ones jointlyproviding an overall vertically broadened sound pattern for eachloudspeaker unit directed principally laterally outwardly and upwardlyof the loudspeaker unit;

FIG. 10B is a side elevational view of the left-hand loudspeaker unit ofFIG. 10A with the individual directive sound patterns of the coneloudspeakers diagrammatically indicated;

FIG. 11 is a sectional of a room with a furniture and loudspeaker takenarrangement utilizing a more sophisticated and expensive form of thepresent invention;

FIG. 12 is a rear perspective view of one of the identical loudspeakerunits shown in FIG. 11;

FIG. 13 is a sectional view of the loudspeaker unit of FIG. 12 takenalong section line 13-43 thereof;

FIG. 14A is a front elevational view of the loudspeaker units shown inFIG. 11 and diagrammatically showing the individual directive soundpatterns of the cone loudspeakers thereof when the rearwardly facingmiddle and outermost cone loudspeakers are energized with the middle andhigh frequencies;

FIG. 14B is a side elevational view of the left-hand loudspeaker unit ofFIG. 13A with the individual directive sound patterns of the coneloudspeakers diagrammatically indicated;

FIG. 15A is a front elevational view of the loudspeaker units shown inFIG. 11 and diagrammatically showing the individual directive soundpatterns of the cone loudspeakers thereof when the rearwardly facingmiddle and innermost cone loudspeakers are energized with middle andhigh frequencies;

FIG. 15B is a side elevational view of the left-hand loudspeaker unit ofFIG. 13A with the individual directive sound patterns of the coneloudspeakers diagrammatically indicated;

FIG. 16A, 16B, 16C, 16D and 16E respectively show five differentenergizing circuit arrangements for the cone loudspeakers used in eachof the loudspeaker enclosures shown in FIGS. 14A and 15A to provide achoice of five different rearwardly directed sound patterns thereof;

FIG. 17 illustrates a switching system and a pair of capacitorsconstituting low-pass filters which provide the five differentenergizing circuit arrangements shown in FIGS. I6A-l6E;

FIG. 18 is a chart illustrating the various frequencies generated by thecone loudspeakers shown in FIGS. l6A-l6E.

Referring now to FIG. 1, a room furniture arrangement as illustratedwherein it is convenient to locate a pair of stereo loudspeaker units 2Aand 2B constituting a preferred form of the invention on tables 4 and 6located on opposite sides of an armchair 8. Normally, such close spacingof stereo loudspeaker units is highly unsatisfactory because ofinadequate separation between the stereo channels acoustically radiatedby the loudspeaker units. However, because of the features of thepresent invention, this close spacing does not become a problem.

Although, as above indicated, the present invention may take a varietyof forms, as illustrated in FIG. I the stereo loudspeaker system thereshown comprises a pair of loudspeaker sections for the two stereochannels involved including relatively closely spaced, small,lightweight, mirror-image loudspeaker units 2A and 2B having loudspeakerenclosures 10a and 10b. The loudspeaker enclosures 10a and 10b includeforwardly and rearwardly directed cone loudspeakers to be described and,in the closely spaced arrangement shown in FIG. 1, the enclosures 10aand 10b are oriented so that the rearwardly directed cone loudspeakerstherein radiate directive middleand high-frequency sounds principallylaterally outwardly and also most advantageously upwardly against avertical sound reflecting wall 11 in front of which the furniture andloudspeaker units illustrated are placed, so that a listener sittingacross the room will receive directly and by reflection off of the soundreflecting wall 11 directively radiated middleand high-frequency stereosound over wide angles with good stereo separation.

FIGS. 2A and 2B show a rear perspective view of the loudspeaker units 2Aand 2B. The details of the right-hand loudspeaker unit 28 'will now bedescribed, it being understood that the other loudspeaker unit 2A is themirror image of the same, and so corresponding portions of theloudspeaker unit 2A and 2B will be given similar reference numbersexcept that a prime has been used with reference numbers for loudspeakerunit 2A. As best shown in FIGS. 23 and 3, the loudspeaker enclosure b isa cube-shaped enclosure having a square vertical front baffle-formingwall 12 and a square bottom wall 14. The front baffle-forming wall 12has an opening 16 therein behind which is mounted a cone loudspeaker 18which directs sound forwardly through the opening 16. An attractivesound transparent cloth 20 covers the front surface of thebaffle-forming wall 12.

The loudspeaker enclosure 10b has truncated vertical sidewalls 22 and 24and a truncated vertical rear wall 26 which define, with a truncatedhorizontal top wall 32, the margins of cube truncating horizontallyspaced baffle-forming walls 28 and 30 which respectively intersect oneanother and form an obtuse angle preferably of about 145 therebetween.The loudspeaker enclosure 10b thus resembles an unsymmetricallytruncated cube.

The baffle-forming walls 28 and 30 incline in an upward direction in theorientation shown in the drawing, the baffleforming wall 28 extending ina plane transverse to the vertical sidewalls 22 and 24 and extending atabout a 45 angle to two reference transverse vertical planes PLl and Pl.2 respectively extending transversely and parallel to the frontvertical wall 12 of the speaker enclosure 10a. The other baffle-formingwall 30 extends at an angle of about 35 with respect to thebaffleforming wall 28. i

The baffle-forming wall 28 has an opening 33 therein behind which issupported a'cone loudspeaker 35 which directs sound through the opening33. The other baffle-forming wall 30 has an opening 39 therein behindwhich is supported a cone loudspeaker 37 which directs sound through theopening 39. A suitable covering of sound transparent cloth 20 is placedover the baffle-forming walls 28 and 30 to improve the appearance of theenclosure.

The cone loudspeakers 35 and 37 radiate at the middle and highfrequencies (that is frequencies of approximately 300 Hertz and higher)directive sound patterns resembling the diagrammatic representations ofthe sound patterns P2 and P3 shown in FIGS. 7A and 7B representing therelative sound intensities at various angles extending from a point atthe base of each sound pattern, as is well known in the art. (Actually,the sound patterns illustrated represent an average directivity patternof these frequencies since the directivity pattern of the middlefrequencies is generally much wider than that illustrated and that ofmost of the high frequencies is narrower than that illustrated.) Theaxes of these directive sound patterns incline rearwardly between about35-45 asymmetrically to a horizontal line parallel to the frontenclosure wall I2 and to a vertical line. The sound patterns from thecone loudspeakers 35 and 37 overlap to provide an overall horizontallybroadened (i.e., a vertically facing fan-shaped) sound pattern directedupwardly and principally laterally outwardly of the loudspeakerenclosure 10b.

As previously indicated, the low-frequency response of a loudspeakersystem is a function of a number of variables including the total coneloudspeaker area efiective in generating low frequencies and the amountof enclosure volume per loudspeaker. The loudspeaker enclosures 10a and10b are sealed enclosures and the cone loudspeakers l8, 18', 35, 35', 37and 37' may be, for example, 4" cone loudspeakers which are fed with allof the frequencies of the associated stereo channel. However, with threesuch small-sized enclosures per stereo loudspeaker section, it is notfeasible to obtain a very good low-frequency response down, for example,to 30 to 40 Hertz. However, a good low-frequency response in the 30- to40- Hertz range can be electrically achieved by using a suitable circuitin the amplifier system involved, as is well known in the art.

One of the main advantages of the stereo loudspeaker units 2A and 2Bjust described is that they provide, in addition to the desirableoverall rearwardly, horizontally broadened, principally upwardly andlaterally outwardly directed sound pattern referred to, three otherrearwardly directed sound pattern configurations to adapt theloudspeaker system illustrated to a variety of different room geometriesand loudspeaker unit placement limitations. Referring, for example, toFIG. 5, there is shown a furniture and loudspeaker unit arrangementwherein the loudspeaker unit 2A and 2B are mounted on tables 4 and 6positioned at the opposite ends of a long sofa 40 adjacent to thesidewall 42-42 ofthe room involved. For this arrangement, loudspeakerunit 2A and 2B are rotated inwardly from the position shown in FIG. 1 asindicated by the change in direction of arrows 43a and 43b positionedadjacent to the reference characters 2A and 2B in FIGS. 1 and 5. In suchcase, it will be apparent that the axes of the rearwardly facing coneloudspeakers 35 and 37 and the directive sound patterns P2 and P3 arevertically spaced and are directed rearwardly and laterally inwardly ofthe enclosure 10b (FIGS. 9A and 9B) to provide an overall verticallybroadened sound pattern inclining principally laterally inwardly of theenclosure 10a.

An overall principally laterally inwardly and upwardly directedhorizontally broadened sound pattern can be achieved by interchangingthe positions of the loudspeaker units 2A and 28 shown in FIG. 7A, sothat the left-hand and right-hand loudspeaker units therein become theright-hand and left-hand loudspeaker units as illustrated in FIGS. 8Aand 8B. (A generally horizontal broadened sound pattern configurationshown in FIGS. 7A or 8A is especially useful, for example, where coneloudspeakers are directed against horizontally broken up reflecting wallsurfaces, as in the case of shelving and the like supported upon thesound reflected wall 11.)

An overall principally laterally outwardly and upwardly directedvertically broadened (i.e. a horizontally facing fanshaped) soundpattern can be achieved by interchanging the left-hand and right-handloudspeaker units 2A and 2B in FIG. 9A to provide the loudspeaker unitarrangement illustrated in FIG. 10A and 10B. 7

Although in the embodiment of the invention just described all of thecone loudspeakers radiate both low, middle and high frequencies, theloudspeaker units 2A and 2B are adaptable to loudspeaker systems whereinthe low nondirective frequencies are generated by special low-frequencyloudspeakers or woofers which may be positioned below, above or to oneside of the loudspeaker units 2A and 2B.

To obtain an even better low-frequency response and to provideadjustability of the directive sound patterns of the loudspeaker unitselectrically, a more sophisticated and expensive loudspeaker system ofthe present invention may be provided as illustrated in FIGS. ll through15. As in the case of the loudspeaker units 2A and 2B, the stereoloudspeaker units now to be described and identified by referencecharacters 2C and 2D are most advantageously made sufficiently compactthat they may be readily placed upon end tables, bookshelves or the likeor even in the open rear portion of a large console cabinet. Physically,the loudspeaker units 2C and 2D are identical (identical elements,however, can also be considered mirror images of one another). However,as will appear electrically and acoustically they are not identicalsince the sound patterns generated by the loudspeaker units 2C and 2Dwill generally provide overall mirror'image, asymmetric, rearwardlydirected sound patterns at the middle and high frequencies extendingprincipally upwardly and laterally outwardly or upwardly and laterallyinwardly of the loudspeaker system. Also, the loudspeaker units 2C and2D directively radiate middle and high frequencies forwardly of theloudspeaker units 2C and 2D. The selection of different rearwardlydirected sound patterns is accomplished by the use of switches andfilters contained in a separate switch housing 41 (FIG. 11) which mayrest on one of the end tables 4 or some other suitable support surface.The housing will contain a multiposition switch with a control knob 41aor the like for selecting one of a number of sound patterns.

Refer now to FIGS. 12 and 13 which best illustrate the construction ofthe left-hand loudspeaker unit 2C, it being understood that loudspeakerunits 2C and 2D are physically identical and so corresponding partsthereof will be identically numbered. (The corresponding parts will berelated and numbered in a mirror-image sense so that the confronting orfacing parts thereof will be considered corresponding parts, etc.)Consequently, loudspeaker unit 2D will not be separately described. Asshown in FIGS. 12 and 13, loudspeaker unit 2C includes an enclosure 43having a front baffle-forming wall 45 with one or more coneloudspeaker-receiving openings 47 (only one being shown). Coneloudspeaker 49 is mounted behind the opening 47. The bafile-forming wall45 joins at the right-hand and left-hand margins thereof verticalsidewalls 51-51" and at the top and bottom margins thereof a horizontaltop wall 53 and a horizontal bottom wall 55. (Primed numbers are usedfor parts of the loudspeaker unit which are positioned on the laterallyoutwardly facing sides thereof.)

A centered rearwardly and upwardly facing rectangular baffie-formingwall 57 making an angle of about 45 to a horizontal plane intersects therear margin of the top wall 53 along a portion of the length thereof,the baffle-forming wall 57 being connected to the bottom wall 55 of theenclosure 43 by a rectangular vertical rear wall 61. The side margins ofthe upwardly and rearwardly facing baffle-forming wall 57 are connectedto the vertical side walls 51-51 respectively by upwardly facingmirror-image related baffle-forming walls 63-63. As illustrated, thebaffle-forming walls 63-63 extend at about a 35 angle with respect tothe adjacent baffle-forming walls. It should be apparent that theangular relationship between each of the baffle-forming walls 63 and 63'and the center baffle-fonning wall 57 is similar to the angularrelationship between the baffle-forming walls 30 and 28 in theembodiment of the invention shown in FIGS. 1 through 10. Themirror-image related baffle-forming walls 63-63 are connected to thebottom wall 55 through vertical lower mirrorimage related baffle-formingwalls 65-65.

Centered within the central rearwardly and upwardly facingbaffle-forming wall 57 is a cone loudspeaker-receiving opening 67 behindwhich is mounted a cone loudspeaker 69. The first mentioned mirror-imagerelated baffle-forming walls 63-63 are provided with coneloudspeaker-receiving openings 71-71 behind which are mounted coneloudspeakers 73-73. The lower mirror-image related baffle-fonning walls65-65 are provided with cone loudspeaker-receiving openings 75-75 behindwhich are mounted cone loudspeakers 77-77.

The various cone loudspeakers 49, 73-73 and 77-77' may be identical coneloudspeakers, such as 4" cone loudspeakers mounted within a commonsealed enclosure space 79. The various bafile-forming walls 45, 57,63-63 and 65-65 may be covered by suitable sound transparent cloth asindicated by reference numeral 8].

Particularly in the embodiment of the invention now being described, itis highly desirable that all of the loudspeakers receive thenondirective low frequencies of the associated stereo channel so thatadvantage can be taken of the increased low-frequency response when thetotal cone area of the low frequency radiating loudspeakers is amaximum.

Two possible directive middleand high-frequency sound patterns generatedby the various loudspeakers 49, 73-73 and 77-77 are illustrated in FIGS.14A, 1413, A and 158. As indicated by these figures, directive middleand high frequencies are fed, in addition to the forwardly directedloudspeaker 49 and centered rearwardly directed loudspeaker 69,selectively to either the outer loudspeakers 73 and 77 or the innerloudspeakers 73 and 77 so that, in addition to a for-- wardly radiateddirective sound pattern at these frequencies, there is provided eitheran overall principally rearwardly, upwardly and outwardly, orrearwardly, upwardly and inwardly directed sound pattern which, unlikethe embodiment of FIGS. l-l0 has both horizontally and vertically spacedcomponents. These overall rearwardly directed sound patterns are, as inthe case of the other embodiment of the invention described, a result ofthe overlapping and reinforcement of individual directive sound patternsP2, P3, and P4 of the cone loudspeakers 73, 69 and 77 in the case ofFIG. 14A, and individual directive sound patterns P2, P3 and P4 of coneloudspeakers 73, 69 and 77 in the case of FIG. 15A. The individualdirective sound patterns P2 and P3 in FIG. 14A and P2 and P3 in FIG. 15Aare horizontally spaced to provide a horizontally broadened soundpattern component and the directive sound patterns P2 and P4 in FIG. 14Aand P2 and P4 in FIG. 15A provide a vertically broadened sound patterncomponent.

In addition to the sound patterns shown in FIG. 14A and 15A, severalother sound patterns can be obtained by applying directive middle andhigh frequencies selectively to other combinations of the rearwardlydirected loudspeakers. One way in which a total of five different soundpattern configurations, including those shown in FIG. 14A and 15A, canbe simply and inexpensively achieved is illustrated in FIGS. l6A-16E,FIG. 17 and FIG. 18 to which reference should now be made.

The voice coils of the various cone loudspeakers described of eachloudspeaker unit may be connected across a pair of stereo inputterminals 80-82 containing the low, middle and high frequencies of theassociated stereo channel in a variety of ways. To simplify theswitching circuitry, the voice coils of the six cone loudspeakersdescribed may be connected in series connected pairs across the stereochannel input terminals 80 and 82 as illustrated in FIGS. l6A-I6E.Accordingly, the voice coils 49a and 69a of the centered forwardly andrearwardly facing cone loudspeakers149 and 69 are connected in seriesacross the input terminals 80 and 82, the voice coils 73a and 73a of themirror-image related loudspeakers 73' and 73 are connected in seriesacross the input terminals 80 and 82, and the voice coils 77a and 77a ofthe mirror-image related loudspeakers 77' and 77 are connected in seriesacross the input terminals 80 and 82.

A suitable low-pass filter, which may be capacitors 84 and 84, areconnected across various ones of the voice coils of the mirror-imagerelated loudspeakers as indicated in FIG. 16A, 16B, 16C and 16D by meansof the switching network shown in FIG. 17. (FIG. 17 shows the switchingnetwork for one of the loudspeaker units 2C, it being understood that anidentical switching network is used and ganged therewith for the otherloudspeaker unit 2D.) The switching network shown in FIG. 17 includestwo ganged switch sections 85 and 85' including movable wipers 85a and850' which respectively make selective contact with stationary contacts85-1 through 85-5 and 85-1 through 85-5', respectively. The movablewiper 85a is connected through the low-pass filter capacitor 84 to thejuncture 89 between the voice coils 73a and 73a. The movable wiper 85ais connected through the low-pass filter capacitor 84' to the juncture89' of the voice coils 77a and 77a. The stereo channel input terminal 80is shown connected to the stationary contacts 854 of the switch section85 and the stationary contact 85-3 and 85-4' of the switch section 85.The stereo channel input terminal 82 is shown connected to thestationary contact 85-1 of the switch Section 85 and stationary contacts85-1 and 85-2' of the switch section 85. When the wipers 85a and 85a aresequentially connected to the various similarly numbered associatedstationary contacts, the four difierent capacitor circuit connectionsshown in FIG. 16A, 16B, 16C and 16D are achieved. In FIGS. 16A, thelow-pass filter capacitors 84 and 84' are respectively connected inparallel with the voice coils 73a and 77a so that the cone loudspeakers73 and 77 do not receive any significant amount of middle and highfrequencies, thereby producing individual overlapping directive soundpatterns from the forwardly directed loudspeaker 49, the centerrearwardly directed speaker 69 and the laterally outwardly facingloudspeakers 73' and 77'.

FlG. 16D shows the low-pass filter capacitors 84 and 84' coupled acrossonly the voice coils 73a and 77a of the loudspeakers 73 and 77 toproduce individual overlapping sound patterns which are the mirror-imageof that just described in connection with FIG. 16A.

In FIG. 16B only voice coil 77a of loudspeaker 77 has a lowpass flltercapacitor 84' connected thereacross so that the overall sound patternachieved by the individual overlapping sound patterns has both laterallyinwardly and laterally outwardly components (but of differentconfiguration) which, although normally not preferred, can be desirableunder certain circumstances. Similarly in FIG. 16C, only the voice coil77a has a low-pass filter capacitor 84 connected thereacross to providea sound pattern which is the mirror-image of that just described inconnection with FIG. 168.

FIG. 16E shows a circuit arrangement where none of the voice coils arebypassed by low-pass filter capacitors. in such case there are directivecomponents generated by all of the loudspeakers which may be desirablefor monaural recordings.

it should be apparent that other switching arrangements may be made toprovide for other selective connections of low-pass filter capacitors tothe loudspeakers. For example, a different switching network couldprovide for connection of the low-pass filters across voice coils 73a,69a and 77a to duplicate the sound pattern provided by the loudspeakerunit arrangement of FIG. A where a vertically broadened (i.e.,horizontally facing fan-shaped) sound pattern extends laterallyoutwardly, Similarly, another switching arrangement could produce themirror image of the sound pattern just described to duplicate the soundpattern provided by the loudspeaker arrangement of FIG. 9A.

It is apparent that the present invention provides an extremelyadaptable stereo loudspeaker system which, unlike the loudspeakersystems of the prior art, can be adapted to a maximum number ofroomgeometry and loudspeaker unit placement conditions.

It should be understood that various modifications may be made in themost preferred form of the invention just described without deviatingfrom the broader aspects of the invention.

lclaim: I

l. in a room havingan upstanding sound reflecting wall, a first sourceof electrical signals of at least middle and high frequencies for afirst stereo channel, and a second source of electrical signals of atleast middle and high frequencies for a second stereo channel, theimprovement comprising a stereo loudspeaker system mounted in front ofsaid wall in spaced relation thereto, said loudspeaker system havinghousing means resting on a horizontal support surface in a predeterminedposition and containing right-hand and left'hand loudspeaker sectionsincluding rearwardly directed loudspeaker means respectively connectedto said first and second sources of electrical signals, the rearwardlydirected loudspeaker means of each section producing an overalldirective sound pattern of the associated middleand high-frequencysignals which is the mirror-image of the rearwardly directed loudspeakermeans of the other section with respect to a centered vertical planeextending transverse to said sound reflecting wall midway between theloudspeaker sections and which overall directive sound. pattern isasymmetrically directed toward said upstanding sound reflecting wall sothe overall directive sound pattern is directed mainly in a directionmaking a substantial angle with both the associated horizontal andvertical planes extending at right angles to said sound reflecting walland passing through the rearwardly directed loudspeaker means producingthe overall directive sound pattern involved, and said housing meansfurther including for each loudspeaker section a forwardly directedloudspeaker means also connected to the associated source of electricalsignals of the associated stereo channel and providing a forwardlydirective sound pattern of said middle and high frequencies whose axisis directed forwardly in a direction generally parallel to said centeredvertical plane.

2. The stereo loudspeaker system of claim 1 wherein said right-hand andleft-hand loudspeaker sections are relatively closely spaced so thatthey are remote from the sidewalls of said room which extends traverselyof said upstanding sound reflecting wall of the room, and saidrearwardly directed loudspeaker means of said right-hand and left-handloudspeaker sections respectively producing respective overallrearwardly directed sound patterns which'are directed principallyoutwardly of the loudspeaker system.

3. The stereo loudspeaker system' of claim 1 wherein said right-hand andleft-hand loudspeaker sections are positioned a substantial distanceapart where they are closer to said sidewalls of the room than thecenter of said wall, and the rearwardly directed loudspeaker means ofsaid right-hand and left-hand loudspeaker sections producing respectiveoverall rearwardly directed sound patterns which are directedprincipally inwardly of the loudspeaker system.

4. The stereo loudspeaker system of claim 1 wherein the overallrearwardly directed sound pattern produced by the rearwardly directedloudspeaker means of each loudspeaker section is fan-shaped so as tohave a cross section much greater in one direction transversely throughthe sound pattern than in the other direction transversely through thesound pattern.

5. The stereo loudspeaker system of claim 1 wherein there is providedmeans for selectively positioning the overall directive sound patternproduced by said rearwardly directed loudspeaker means of eachloudspeaker section so it is directed selectively principally laterallyoutwardly or inwardly of the loudspeaker system.

6. In a room having an upstanding sound reflecting wall, a first sourceof electrical signals of at least middle and high frequencies for afirst stereo channel, and a second source of electrical signals of atleast middle and high frequencies for a second stereo channel, theimprovement comprising a stereo loudspeaker system mounted in front ofsaid wall in spaced relation thereto, said loudspeaker system havingright-hand and left-hand loudspeaker sections each including a separateloudspeaker enclosure having rearwardly directed loudspeaker meansconnected to a different one of said sources of electrical signals andproviding an overall sound pattern directed rearwardly against saidsound reflecting wall, said loudspeaker enclosure of each loudspeakersection being readily supportable on a horizontal support surface in twodifferent orthogonally related positions where said overall soundpattern of said rearwardly directed loudspeaker means is directedrespectively principally laterally outwardly and principally laterallyinwardly of a vertical plane extending transversely to said soundreflecting wall and passing through the walls of the rearwardly directedloudspeaker means producing the overall sound pattern involved.

7. In a room having an upstanding sound reflecting wall, a

first source of electrical signals of at least middle and highfrequencies for a first stereo channel, and a second source ofelectrical signals of at least middle and high frequencies for a secondstereo channel, the improvement comprising a stereo loudspeaker systemmounted in front of said wall in spaced relation thereto, saidloudspeaker system having housing means resting on a horizontal supportsurface in a predetermined position and containing right-hand andleft-hand loudspeaker sections each including first and secondrearwardly directed loudspeaker means, each of said first and secondrearwardly directed loudspeaker means producing an overall directivesound pattern directed asymmetrically rearwardly towards said soundreflecting wall in the opposite lateral direction from the other of sameso the overall directive sound patterns produced by each of said firstand second rearwardly directed loudspeaker means is directed mainly indirections making a substantial angle with the associated vertical planepassing through the sound pattern involved, and means for selectivelycoupling the middle and high frequencies of said signal sources to thefirst or second rearwardly directed loudspeaker means of eachloudspeaker section.

8. In a room having an upstanding sound reflecting wall, a first andsecond source of electrical signals of two stereo channels encompassingat least the middleand high-frequency range where acoustically directedsound signals. are directive, a stereo loudspeaker system mounted infront of an upstanding sound reflecting wall in spaced relation thereto,said loudspeaker system having a right-hand and a left-hand loudspeakersection with rearwardly directed loudspeaker means respectivelyconnected to said first and second sources of electrical signals, saidrearwardly directed loudspeaker means of said right-hand and left-handloudspeaker sections being positioned near the sidewalls of said room,and the rearwardly directed loudspeaker means of each section providingan overall directive sound pattern which is the mirror image of theloudspeaker means of the other section and is directed 7 only inwardlytoward said upstanding wall to reflect off the central portion of saidwall into the listening area.

9. In combination, first and second source of electrical signalsconstituting the two channels of a stereo system and encompassing atleast the middle and high frequencies of the signal channels involved, aloudspeaker system spaced adjacent but in spaced relation to anupstanding sound reflecting wall of a room and comprising right-hand andleft-hand stereo loudspeaker sections respectively for directivelyradiating signals of said stereo channels and which are mirror images ofone another with respect to a centered vertical plane extendingtransverse to said sound reflecting wall midway between the loudspeakersections, each loudspeaker section having a separate housing resting ona horizontal support surface which housing includes both forwardly andrearwardly directed loudspeaker means all connected to the saidassociated source of electrical signals, the rearwardly directedloudspeaker means of each loudspeaker section providing an overalldirective sound pattern which is asymmetrically related to an associatedvertical plane extending transversely to said upstanding wall so theoverall directive sound pattern thereof is directed mainly in directionsmaking a substantial angle with the associated vertical plane passingthrough the sound pattern involved, wherein directive signals for eachstereophonic channel are directed both forwardly into the room andrearwardly mainly either laterally inwardly or outwardly of saidassociated vertical plane, where they reflect off of said upstandingwall.

10. The combination of claim 9 wherein said first and second sources ofelectrical signals include low frequencies as well as middle and highfrequencies, wherein the forwardly and rearwardly directed loudspeakermeans act as full-range sound radiating means.

11. In combination, first and second sources of electrical signalsconstituting the two channels of a stereo system and encompassing atleast the middle and high frequencies of the signal channels involved, aloudspeaker system spaced adjacent but in spaced relation to anupstanding sound reflecting wall of a room and comprising right-hand andlefthand stereo loudspeaker sections respectively for directivelyradiating Y signals signal channels including signals in at least themiddle and high frequencies which are directively acoustically radiatedthereby, all of the rearwardly directed loudspeaker means of eachloudspeaker section providing an overall directive sound pattern whichis asymmetrically related to an associated vertical plane which is toextend at right angles to said vertical wall and passing through theoverall directive sound pattern involved so the overall directive soundpattern thereof is directed mainly in directions making a substantialangle with the associated vertical plane passing through the soundpattern involved, and said forwardly directed loudspeaker means havingdirective sound patterns which are generally parallel to one another andto said centered vertical plane, so directive signals for each stereochannel are directed both forwardly into the room and rearwardly eitherinwardly or outwardly of said associated vertical plane.

12. A stereo loudspeaker system to be positioned adjacent but in spacedrelationship to a vertical sound reflecting wall of a room, saidloudspeaker system having housing means adapted to be supported on ahorizontal support surface and containing right-hand and left-handloudspeaker sections which are mirror images of one another with respectto a centered vertical plane extending transverse to said soundreflecting wall midway between the loudspeaker sections, eachloudspeaker section having forwardly and rearwardly directed loudspeakermeans to be connected to one of two stereo signal channels includingsignals in at least the middle and high frequencies which aredirectively acoustically radiated thereby, all of the rearwardlydirected loudspeaker means of each loudspeaker section providing anoverall directive sound pattern which is asymmetrically related to anassociated vertical plane which is to extend at right angles to saidvertical wall and passing through the overall directive sound patterninvolved so the overall directive sound pattern thereof is directedmainly in directions making a substantial angle with the associatedvertical plane passing through the sound pattern involved, and saidforwardly directed loudspeaker means having directive sound patternswhich are generally parallel to one another and to said centeredvertical plane, so directive signals for each stereo channel aredirected both forwardly into the room and rearwardly either inwardly oroutwardly of said associated vertical plane.

13. The stereo loudspeaker system of claim 12 wherein all of saidloudspeaker means of each loudspeaker section being mounted in aseparate portable enclosure of a size and weight readily to be placedupon a table, bookshelf or the like.

14. The stereo loudspeaker system of claim 13 wherein the commonenclosure of each loudspeaker section can be supported in either one oftwo orthogonally related positions wherein the axis of the overallrearwardly directive sound pattern thereof extends substantially at anangle either outwardly or inwardly of said associated vertical plane.

15. A stereo loudspeaker system to be placed in adjacent spaced relationto a vertical sound reflecting wall, said loudspeaker system comprising:housing means placeable on a horizontal support surface and containing aright-hand and left-hand stereo loudspeaker section for receivingrespectively at least the middle and high frequency electrical signalsof two stereo channels and which are mirror images of one another withrespect to a centered vertical plane extending transverse to said soundreflecting wall midway between the loudspeaker sections, eachloudspeaker section when said housing means is supported on saidhorizontal support surface in front of said sound reflecting wall havingforwardly and rearwardly directed loudspeaker means to be respectivelyconnected to a source of stereo signals including said middle and highfrequencies which are to be directively acoustically radiated thereby,said rearwardly directed loudspeaker means of each loudspeaker sectionproviding'an overall directive sound pattern which is asymmetricallyrelated to both a horizontal plane and a vertical plane which extendsbetween the front and rear of said housing means, so the overallrearwardly directed sound pattern of each loudspeaker section isdirected rearwardly principally in a direction inclining substantiallyin an upward or downward direction extending either substantiallylaterally outwardly or inwardly of said associated vertical plane.

16. The stereo loudspeaker system of claim 15 wherein said rearwardlydirected loudspeaker means of each loudspeaker section comprises atleast two loudspeaker units having overlapping directive patternsforming an overall directive sound pattern which is fan-shaped so as tohave a cross section much greater in one direction transversely throughthe sound pattern than in the other direction transversely through thesound pattern.

17. The stereo loudspeaker system of claim 16 wherein the axes of saidoverlapping directive sound patterns of the loudspeaker units of eachloudspeaker section form an acute angle.

18. A stereo loudspeaker system to be placed near a vertical soundreflecting wall in a room, said stereo loudspeaker system comp-rising aright-hand and a left-hand loudspeaker sections which are mirror imagesof one another with respect to a centered vertical plane extendingtransverse to said sound reflecting wall midway between the loudspeakersections; each loudspeaker section including a common speaker enclosurehaving a bottom portion to be placed upon a floor, table or the like,the enclosure having outer enclosure-forming walls defining a sealedenclosure space, said enclosure-forming walls including at the rear endportion thereof a first upwardly rearwardly and laterally facingbaffle-forming wall with a cone loudspeaker-receiving opening thereinand a second rearwardly facing baffle-forming wall with a conespeaker-receiving opening therein and making an obtuse angle withrespect to said first baffle-forming wall, and cone loudspeakers mountedwithin a said sealed enclosure space behind said oneloudspeaker-receiving openings of said first and second baffleformingwalls.

19. The stereo loudspeaker system of claim 18 wherein said commonenclosure of each loudspeaker section is portable and easy to manipulateand has a pair of outer support walls substantially right angles to oneanother upon which the enclosure may be selectively supported in twodifferent positions where said first and second laterally facingbaffle-forming walls then respectively face in opposite rearwardly andlaterally facing directions.

20. The stereo loudspeaker system of claim 18 wherein said first andsecond baffle-forming walls of each enclosure are horizontally spacedfrom one another, said common enclosure of each loudspeaker section hasa support wall upon which the enclosure may be supported when theenclosure is turned about a horizontal axis extending between the frontand rear of the enclosure where said first laterally facingbaffle-forming wall then faces rearwardly in the opposite lateraldirection and said first and second baffle-forming walls aresubstantially vertically spaced fromone another.

21. The stereo loudspeaker system of claim 18 wherein said first andsecond baffle-forming walls of each enclosure are horizontally spacedfrom one another, said first baffle-forming wall makes a substantialangle to mutually perpendicular vertical planes extending respectivelylaterally and from the front to the rear of the enclosure, and saidsecond baffle-forming wall extends substantially transverse to thelatter plane and at a substantial angle to the former plane.

22. The stereo loudspeaker system of claim 21 wherein said first andsecond baffle-forming walls of the enclosure of each loudspeaker sectionintersect one another.

23. The stereo loudspeaker system of claim 21 wherein each speakerenclosure has a front vertical baffle-forming wall with a coneloudspeaker receiving opening therein and a cone loudspeaker mountedbehind the same for directing middle and high frequencies forwardly intothe room.

24. A stereo loudspeaker system to be placed in front of a verticalsound reflecting wall of a room, said loudspeaker system comprising: aright-hand and a left-hand loudspeaker section which are mirror imagesof one another with respect to a centered vertical plane extendingtransverse to said sound reflecting wall midway between the loudspeakersections, each loudspeaker section comprising a common speaker enclosurehaving a bottom wall which establishes two orthogonal reference verticalplanes which are to extend respectively parallel and transversely tosaid vertical sound reflecting wall, said enclosure having a first pairof corresponding mirrorimage related rearwardly and upwardly facingbaffle-forming walls which face in opposite lateral directions, acentered rearwardly and upwardly facing baffle-forming wall ositionedbetween said irst pair of mirror-image related ba e-forming

1. In a room having an upstanding sound reflecting wall, a first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having housing means resting on a horizontal support surface in a predetermined position and containing right-hand and left-hand loudspeaker sections including rearwardly directed loudspeaker means respectively connected to said first and second sources of electrical signals, the rearwardly directed loudspeaker means of each section producing an overall directive sound pattern of the associated middle- and high-frequency signals which is the mirror-image of the rearwardly directed loudspeaker means of the other section with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections and which overall directive sound pattern is asymmetrically directed toward said upstanding sound reflecting wall so the overall directive sound pattern is directed mainly in a direction making a substantial angle with both the associated horizontal and vertical planes extending at right angles to said sound reflecting wall and passing through the rearwarDly directed loudspeaker means producing the overall directive sound pattern involved, and said housing means further including for each loudspeaker section a forwardly directed loudspeaker means also connected to the associated source of electrical signals of the associated stereo channel and providing a forwardly directive sound pattern of said middle and high frequencies whose axis is directed forwardly in a direction generally parallel to said centered vertical plane.
 2. The stereo loudspeaker system of claim 1 wherein said right-hand and left-hand loudspeaker sections are relatively closely spaced so that they are remote from the sidewalls of said room which extends traversely of said upstanding sound reflecting wall of the room, and said rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections respectively producing respective overall rearwardly directed sound patterns which are directed principally outwardly of the loudspeaker system.
 3. The stereo loudspeaker system of claim 1 wherein said right-hand and left-hand loudspeaker sections are positioned a substantial distance apart where they are closer to said sidewalls of the room than the center of said wall, and the rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections producing respective overall rearwardly directed sound patterns which are directed principally inwardly of the loudspeaker system.
 4. The stereo loudspeaker system of claim 1 wherein the overall rearwardly directed sound pattern produced by the rearwardly directed loudspeaker means of each loudspeaker section is fan-shaped so as to have a cross section much greater in one direction transversely through the sound pattern than in the other direction transversely through the sound pattern.
 5. The stereo loudspeaker system of claim 1 wherein there is provided means for selectively positioning the overall directive sound pattern produced by said rearwardly directed loudspeaker means of each loudspeaker section so it is directed selectively principally laterally outwardly or inwardly of the loudspeaker system.
 6. In a room having an upstanding sound reflecting wall, a first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having right-hand and left-hand loudspeaker sections each including a separate loudspeaker enclosure having rearwardly directed loudspeaker means connected to a different one of said sources of electrical signals and providing an overall sound pattern directed rearwardly against said sound reflecting wall, said loudspeaker enclosure of each loudspeaker section being readily supportable on a horizontal support surface in two different orthogonally related positions where said overall sound pattern of said rearwardly directed loudspeaker means is directed respectively principally laterally outwardly and principally laterally inwardly of a vertical plane extending transversely to said sound reflecting wall and passing through the walls of the rearwardly directed loudspeaker means producing the overall sound pattern involved.
 7. In a room having an upstanding sound reflecting wall, a first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having housing means resting on a horizontal support surface in a predetermined position and containing right-hand and left-hand loudspeaker sections each including first and second rearwardly directed loudspeaker means, each of said First and second rearwardly directed loudspeaker means producing an overall directive sound pattern directed asymmetrically rearwardly towards said sound reflecting wall in the opposite lateral direction from the other of same so the overall directive sound patterns produced by each of said first and second rearwardly directed loudspeaker means is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and means for selectively coupling the middle and high frequencies of said signal sources to the first or second rearwardly directed loudspeaker means of each loudspeaker section.
 8. In a room having an upstanding sound reflecting wall, a first and second source of electrical signals of two stereo channels encompassing at least the middle- and high-frequency range where acoustically directed sound signals are directive, a stereo loudspeaker system mounted in front of an upstanding sound reflecting wall in spaced relation thereto, said loudspeaker system having a right-hand and a left-hand loudspeaker section with rearwardly directed loudspeaker means respectively connected to said first and second sources of electrical signals, said rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections being positioned near the sidewalls of said room, and the rearwardly directed loudspeaker means of each section providing an overall directive sound pattern which is the mirror image of the loudspeaker means of the other section and is directed only inwardly toward said upstanding wall to reflect off the central portion of said wall into the listening area.
 9. In combination, first and second source of electrical signals constituting the two channels of a stereo system and encompassing at least the middle and high frequencies of the signal channels involved, a loudspeaker system spaced adjacent but in spaced relation to an upstanding sound reflecting wall of a room and comprising right-hand and left-hand stereo loudspeaker sections respectively for directively radiating signals of said stereo channels and which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section having a separate housing resting on a horizontal support surface which housing includes both forwardly and rearwardly directed loudspeaker means all connected to the said associated source of electrical signals, the rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to an associated vertical plane extending transversely to said upstanding wall so the overall directive sound pattern thereof is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, wherein directive signals for each stereophonic channel are directed both forwardly into the room and rearwardly mainly either laterally inwardly or outwardly of said associated vertical plane, where they reflect off of said upstanding wall.
 10. The combination of claim 9 wherein said first and second sources of electrical signals include low frequencies as well as middle and high frequencies, wherein the forwardly and rearwardly directed loudspeaker means act as full-range sound radiating means.
 11. In combination, first and second sources of electrical signals constituting the two channels of a stereo system and encompassing at least the middle and high frequencies of the signal channels involved, a loudspeaker system spaced adjacent but in spaced relation to an upstanding sound reflecting wall of a room and comprising right-hand and left-hand stereo loudspeaker sections respectively for directively radiating signals signal channels including signals in at least the middle and high frequencies which are directively acoustically radiated thereby, all of the rEarwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to an associated vertical plane which is to extend at right angles to said vertical wall and passing through the overall directive sound pattern involved so the overall directive sound pattern thereof is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and said forwardly directed loudspeaker means having directive sound patterns which are generally parallel to one another and to said centered vertical plane, so directive signals for each stereo channel are directed both forwardly into the room and rearwardly either inwardly or outwardly of said associated vertical plane.
 12. A stereo loudspeaker system to be positioned adjacent but in spaced relationship to a vertical sound reflecting wall of a room, said loudspeaker system having housing means adapted to be supported on a horizontal support surface and containing right-hand and left-hand loudspeaker sections which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section having forwardly and rearwardly directed loudspeaker means to be connected to one of two stereo signal channels including signals in at least the middle and high frequencies which are directively acoustically radiated thereby, all of the rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to an associated vertical plane which is to extend at right angles to said vertical wall and passing through the overall directive sound pattern involved so the overall directive sound pattern thereof is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and said forwardly directed loudspeaker means having directive sound patterns which are generally parallel to one another and to said centered vertical plane, so directive signals for each stereo channel are directed both forwardly into the room and rearwardly either inwardly or outwardly of said associated vertical plane.
 13. The stereo loudspeaker system of claim 12 wherein all of said loudspeaker means of each loudspeaker section being mounted in a separate portable enclosure of a size and weight readily to be placed upon a table, bookshelf or the like.
 14. The stereo loudspeaker system of claim 13 wherein the common enclosure of each loudspeaker section can be supported in either one of two orthogonally related positions wherein the axis of the overall rearwardly directive sound pattern thereof extends substantially at an angle either outwardly or inwardly of said associated vertical plane.
 15. A stereo loudspeaker system to be placed in adjacent spaced relation to a vertical sound reflecting wall, said loudspeaker system comprising: housing means placeable on a horizontal support surface and containing a right-hand and left-hand stereo loudspeaker section for receiving respectively at least the middle and high frequency electrical signals of two stereo channels and which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section when said housing means is supported on said horizontal support surface in front of said sound reflecting wall having forwardly and rearwardly directed loudspeaker means to be respectively connected to a source of stereo signals including said middle and high frequencies which are to be directively acoustically radiated thereby, said rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to both a horizontal plane and a vertical plane wHich extends between the front and rear of said housing means, so the overall rearwardly directed sound pattern of each loudspeaker section is directed rearwardly principally in a direction inclining substantially in an upward or downward direction extending either substantially laterally outwardly or inwardly of said associated vertical plane.
 16. The stereo loudspeaker system of claim 15 wherein said rearwardly directed loudspeaker means of each loudspeaker section comprises at least two loudspeaker units having overlapping directive patterns forming an overall directive sound pattern which is fan-shaped so as to have a cross section much greater in one direction transversely through the sound pattern than in the other direction transversely through the sound pattern.
 17. The stereo loudspeaker system of claim 16 wherein the axes of said overlapping directive sound patterns of the loudspeaker units of each loudspeaker section form an acute angle.
 18. A stereo loudspeaker system to be placed near a vertical sound reflecting wall in a room, said stereo loudspeaker system comprising a right-hand and a left-hand loudspeaker sections which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections; each loudspeaker section including a common speaker enclosure having a bottom portion to be placed upon a floor, table or the like, the enclosure having outer enclosure-forming walls defining a sealed enclosure space, said enclosure-forming walls including at the rear end portion thereof a first upwardly rearwardly and laterally facing baffle-forming wall with a cone loudspeaker-receiving opening therein and a second rearwardly facing baffle-forming wall with a cone speaker-receiving opening therein and making an obtuse angle with respect to said first baffle-forming wall, and cone loudspeakers mounted within a said sealed enclosure space behind said one loudspeaker-receiving openings of said first and second baffle-forming walls.
 19. The stereo loudspeaker system of claim 18 wherein said common enclosure of each loudspeaker section is portable and easy to manipulate and has a pair of outer support walls substantially right angles to one another upon which the enclosure may be selectively supported in two different positions where said first and second laterally facing baffle-forming walls then respectively face in opposite rearwardly and laterally facing directions.
 20. The stereo loudspeaker system of claim 18 wherein said first and second baffle-forming walls of each enclosure are horizontally spaced from one another, said common enclosure of each loudspeaker section has a support wall upon which the enclosure may be supported when the enclosure is turned about a horizontal axis extending between the front and rear of the enclosure where said first laterally facing baffle-forming wall then faces rearwardly in the opposite lateral direction and said first and second baffle-forming walls are substantially vertically spaced from one another.
 21. The stereo loudspeaker system of claim 18 wherein said first and second baffle-forming walls of each enclosure are horizontally spaced from one another, said first baffle-forming wall makes a substantial angle to mutually perpendicular vertical planes extending respectively laterally and from the front to the rear of the enclosure, and said second baffle-forming wall extends substantially transverse to the latter plane and at a substantial angle to the former plane.
 22. The stereo loudspeaker system of claim 21 wherein said first and second baffle-forming walls of the enclosure of each loudspeaker section intersect one another.
 23. The stereo loudspeaker system of claim 21 wherein each speaker enclosure has a front vertical baffle-forming wall with a cone loudspeaker receiving opening therein and a cone loudspeaker mounted behind the same for directing middle and high frequencies forwardly into the rOom.
 24. A stereo loudspeaker system to be placed in front of a vertical sound reflecting wall of a room, said loudspeaker system comprising: a right-hand and a left-hand loudspeaker section which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section comprising a common speaker enclosure having a bottom wall which establishes two orthogonal reference vertical planes which are to extend respectively parallel and transversely to said vertical sound reflecting wall, said enclosure having a first pair of corresponding mirror-image related rearwardly and upwardly facing baffle-forming walls which face in opposite lateral directions, a centered rearwardly and upwardly facing baffle-forming wall positioned between said first pair of mirror-image related baffle-forming walls, cone speaker-receiving openings in the aforementioned baffle-forming walls, cone speakers mounted within said enclosure behind said cone speaker-receiving openings for directing sound through said openings, and means for feeding low nondirective frequencies to all of said cone speakers in each enclosure but selectively feeding the middle and high directive frequencies to various ones of the cone speakers of each enclosure to obtain a selection of directive sound patterns from the enclosure. 